The Leica 90mm f/2 APO-Summicron-R ASPH was used, which is optically identical to the Leica 90mm f/2 APO-Summicron-M ASPH. The R version has the advantage of being directly usable on Leica M or Canon with a lens adapter, or convertible to Nikon mount, and I prefer its ergonomics over the M version.